Science Revision Biology 新加坡初二生物

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1、Sec2ScienceRevisionBiologyChapterD4MovementofSubstancesIntoandOutofcellsThemovementofsubstancesinandoutofthecellsoccursinthreeways:Diffusion,Osmosis(passiveprocess)andActiveTransport(requiredenergy).Diffusionisthemovementofparticlesfromaregionofhigherconcentrationtoaregio

2、noflowerconcentrationdownaconcentrationgradient.Diffusionbetweentwosolutionstopswhenthesolutionshomogeneous.Partiallypermeablemembranes---donotallowallmoleculestopassthroughOsmosisisthemovementofwatermoleculesfromaregionofhigherwaterpotentialtoaregionoflowerwaterpotential

3、throughapartiallypermeablePlantsabsorbnutrientsthroughthediffusionprocessandwaterthroughtheosmosisprocessWatermoleculesmovefromadilutedsolutiontoaconcentratedsolutionduringosmosisCarbondioxidediffuseintoaleafcellwhileoxygendiffuseoutofitduringthephotosynthesisprocessOsmos

4、isDiffusionItinvolvesthemovementofwatermoleculesonlyItinvolvesthemomentofanymoleculesTakeplacethroughasemi-permeablemembraneTakeplacewithorwithoutasemi-permeablemembraneOsmosis:~Plantcell-inwater[waterentercell](thecellbecometurgid)-inconcentratedsugarsolution[waterleaves

5、cell](thecellbecomessoft)~Animalcell-inwater[waterenterscellcontinuously](thecellswellsandeventuallybursts)-inconcentrated[waterleavescell](thecellshrinkstoasmallsize)Diffusioninlivingorganisms--unicellularorganisms--photosynthesis--thehumanbodyOsmosisinlivingorganisms--r

6、oots--stemsandleaves--sprayingfruitsActiveTransport--substancesmovefromaregionoflowerconcentrationtoaregionofhigherconcentrationD5TransportinLivingThingsPlantsabsorbwaterthroughosmosis.Transpirationonlytakesplaceinplants.Hearts--anorganwhichpumpsbloodroundthebody--pumpblo

7、odtoallpartsofthebodyBlood--aliquidwhichcarriesmaterials--redbloodcells,platelets,bloodplasma,whitebloodcellsComponentFunctionRedBloodCells红血球~carryoxygenfromthelungtovariouspartsofthebody~containhaemoglobintohelpthemtransportoxygenmoreefficiently~carriesasmallamountofcar

8、bondioxideforremovalPlatelets血小板~preventbloodlossfromdamagedbloodvesselsbyformingclotsBloodPlasm